On long-haul flights airlines rarely exceed this pitch by more than a few inches.

On budget and charter aircraft, the legroom provision can be even grimmer. Some barely surpass the legal minimum.

Population growth

The Civil Aviation Authority is re-examining its rules on cabin spacing, fearing that Britons are fast outgrowing the seats provided for them.

Travellers, particularly the tall, hoping to supplement the meagre pitch of their seat by stretching out into an empty neighbouring slot are increasingly being disappointed.

As are those banking on aisle or emergency exit seats. The airlines have become adept at filling their aircraft to capacity, says Dr George Williams from Cranfield University's College of Aeronautics.

Economy deluxe: Big seat with no frills

"Before the industry was deregulated, aircraft were usually operating at around two-thirds full. Today, at peak times, there can be almost no spare seats. On average they are around 75% full."

Dr Williams says airlines have changed their ticketing to "extract as much revenue as possible" from each flight.

With as many as 100 different fares on offer for the same route - all with their own special restrictions - there is seat price to suit every pocket.

Low cost and student fares have tempted many of those with modest incomes into the "jet set".

Row to go

Several UK airlines maintain that these passengers will choose cheap, cramped seats over spacious, and thus more costly, ones.

American Airlines has vowed to remove two rows of seats from its jets, giving each economy passenger an egalitarian extra five inches of space.

Other airlines are allowing passengers to buy their way to comfort.

Big plane, more legroom?

"Some are introducing economy deluxe seating - business class seats without the other frills business passengers enjoy," says Dr Williams.

The price premium paid by economy "plus" flyers more than makes up for the loss of a few cheap, cramped seats. The weight saving of losing budget travellers, their luggage and meals also makes economic sense for the carriers.

Dr Williams says the arrival of wide-bodied airliners, such as the Airbus A3XX super jumbo, will give economy passengers more space in which to get up and stretch their legs.

Whether airlines will actually place the seats further apart is another matter.

Perk wars

The plight of those who occupy today's economy class is perhaps made harder to tolerate considering the airlines' battle over upper class perks.

The companies spent as much as $4bn last year vying for the lucrative business traveller.

For example, Qantas gives its business passengers 50 inches of pitch.

Deep sleep: A dream for economy flyers

Fully reclining "bedseats" are also on offer. British Airways was told by NASA experts humans can only enter refreshing REM sleep when prone, so it introduced the "mini-sleeper".

For those closer to the aircraft's tail, the only hope of getting to sleep may be to count the pounds the cheap seat has saved them.